Preparing phosphate charging stock



--- Nr w smes PATENT, OFFICE *Thista pplication is Patented 4, 1936 I,

' 1,132,029,309 PREPARING rnosrim'rn CHARGING STOC 7 Harry A Curtis, Knoxville, Tenn and Armand J. Abrams, Colbert County, near Sheffield, Alas, assign'ors to Tennessee V alley Authority, Wilson Dam, Ala., a corporation l No nmwih fl Application August 22, 1934, i Q -Serial No. "140,968 i H "13 Clain1s., (ores-223) (Granted under the act of March 3, i883, as

Aprilu30; 1928, and the invention herein 'dethereon.

This invention relates to the processof prelparing fine, solid chemical materialsfor-incorporationin the. charging stockof metallurgical furnaces and particularly the treatment Qf'fine phosphate rock for incorporation in phosphorus reductionfurnace charging stock.

Oneof the objects of this invention to provide a means for-the combining of fine, solid chemical materials, including oresv and other, metallurgical furnace charging stock constituents,

in order that they maybe. in suitable physical condition to include in such. charging stocks.

of suflicient size for incorporation in phos'phornace operations.

"itself, provided proper chemical material, such Another object of thisinvention is the provision :for a continuous process for the agglomeration-of fine phosphate rock to make particles us reduction furnace charging stock.- j

vision for a means of modifyihgthe coking properties'of coking coal in order that the coke so produced may be suitable for metallurgical fur- Other objects of this invention include the provision for a means'for thecarbonization of COk-"r ing coal at lowtemperatures.

Wehave found that, by heatingiine, solid as sand, cokefbreeze, phosphate rock and other ,metallurgicalfurnace charging stock constituents,c.which'are not volatilized at the temperature ofheating, to a teming, it coal to the heated fine material, and by m. mixing the finejcoal and heated fine material .through the plastic stage of the"'coal, a partial carbonization of, the; coal .to semi-coke' takes place. The resulting, material while still in a" heated statemay be densifled by compression, suchas by a'passing between rolls, and'the carbonization of the densified mixture may be com-, pleted by, utilizingthe residual coking properties of the semigcoke. The resulting material has -been found to be of suflicijent size and hardness touse asaconstituent of a metallurgical furnace chargingstock or to constitute the charging stock proportions of original ingredients were used tofresult in the correct proportions in the final mixture. I 1 One example of the operation of our process is given for theagglomeration'of fine phosphate amended April so, 1928; s10 o. G. 7:57)

rock so that the resulting mixture may be used i as a constituent of a phosphorus reductionfurscribed, if patented, may be manufactured and used by or for thejGovernment for governmental purposeswithout the payment to us of any royalty nace charging stock. Fine Tennessee brown phosphate rock of: less than twenty mesh, may be fheated. at 850 C. while being agitated continu 5 I ously and'conveyed to a mixer. A fine coking coal C of less than twenty mesh may be'heated at, 170

C. while being agitated continuously'and conveyed tothe same mixer. The hot fine coalmay-be conveyed into thehot fine phosphate rock in the ratiosof 1 part to 3.7 parts by weight and the resulting mixture at approximately 620 C(may be conveyed and agitated continuously until the mixture isuniformly black and plastic. In this condition, the hot mixture maybe subjected to compression by passing between heated; rolls in order to densify the mixture .and preserve the residualzcoking properties ofthe agglomerated mass The densified material may be carbonized further, to establish the possibility of utilizing its residual coking power by heating at "650 to 1 Another example of theoperation oi proc- Another object of this invention is the pro-' ess is given for the agglomeration of a mixture of fine phosphate rockandfine silica. so that the resulting product maybe used as a phosphorus reduction charging stock. Fine Tennessee phosphate rock may be nnxedwithlfine silica in the ratio of 883 parts: to 11,7,parts. by weight and the mixture may be heate d to 850 C. and agitated continuously and conveyed to the mixer. A fine coking coal may be heated to 170 Qwhile being agitated continuously and conveyed to the same mixer. The hot,fine coal may be added continuously to the hot mixture of fine. phosphate rockand-.-fine silica in the ratio of 1 part to $5 parts and the resulting mixture furthenprocessed asin the foregoing example.

It isevident that there are numerous factors which willinfluence the conditions for the, most satisfactory operation of our process, the actual limits of which cannot be established except by detailed study of each set of raw materials and finished products involved.

r The fine, solid chemical me watt may be agglomerated, v includes any fine material,

vvhich may not be appreciably volatilized at the temperature of heating, eveniffit is 'required in certain instances ,to maintain an inert atmosphere during the heating period. The fine "material should preferably be less thanften mesh,

l with more effective heat transfer being obtained with much finer material. The temperature of heating for the fine, solid chemical material may vary but for all materials so far investigated we 5 of the weights of coal to the weights of materials I being agglomerated may vary from 1 to 2 to l to 10 but the preferred ratio is approximately 1 to 4 for the materials which have so far been investigated. The coal which has been freshly mined is preferred, in order that there has been no appreciable oxidation during the period of storage. The fine coal may be used without a preliminary heating or may be heated to a reasonable degree, so long as the heating conditions are such that no appreciable oxidation of the coal takes place.

When it is desired to preheat the coal, it has been found-that temperatures between and C. are effective, both as a means of reducing the moisture content of, the coal somewhat and as a means of supplying some heat to the subsequent mixture by having the coal above atmospheric temperatures and still below any possible coking temperatures of the coal. It is necessary in every instance to add the fine coal or the fine pre-heated coal to the relatively highly heated solid chemical material which is to be agglomerated.

The fine, solid chemical material to be agglomerated may most conveniently be heated during continuous conveying and stirring to obtain good heat transfer. When the proper temperature of this heated material has been reached, the fine coal, either with or without preheating, may be added to the heated material and the mixing continued until the resulting mixture contains an appreciable quantity of semicoke.

V In certain instances the heated material to be agglomerated may be cooled below the maximum heating temperature before the fine coal is added I to obtain the maximum benefit of the coal during its period of plasticity. In other instances, a small amount of additional heat may have to be added to maintain the temperature of the mixture at the optimum for the proper carbonization of the coal in the mixture. be suitably varied so that the temperature of the resulting mixture will be from 600 to 750 C.

Ordinarily, it is preferred to utilize only a por-' tion of the coking properties of the coal up to this point, in viewof the fact that, in certain instances, it is desirable to treat the semi-plastic mass under pressure, such as between rolls, to densify the porous mixture. The resulting densified mixture may be used as such or may be further carbonized by conventional means. The

materials, such as minerals and materials of high,

as well as intermediate states of purity, limited in this application to those materials which are not appreciably volatilized at the temperature of heating in the respective steps of the process involved, with or without being maintained in an Rates of feed may inert atmosphere. The solid chemical materials include metallic and non-metallic ores, acidic and basic materials used as fluxes and carbonaceous materials which may be agglomerated separately or in mixtures for use as constituents of the charge or constitute the charge for metallurgical furnaces.

We claim:

1. Process of preparing phosphorus reduction furnace charging stock which comprises mixing fine phosphate rock and fine silica, heating the mixture of fine phosphate rock and fine silica to a,:temperature below the sintering point of the mixture, heating fine coking coal, adding the hot fine coking coal to the hot unsintered mixture of fine phosphate rock and fine silica, mixing the coal, phosphate rock and silica untilthe mixture contains semi-coke, passing the mixture containing semi-coke between rolls to increase its apparent density and completing the carbonization H of densified mixture.

2. Process of preparing phosphorus reduction furnace charging stock which comprises heating a mixture of fine phosphate rock and fine silica to a temperature below the sintering point of the mixture, adding hot fine coking coal to the hot unsintered mixture of fine phosphate rock and fine silica, mixing the coal, phosphate rock and silica until the mixture contains semi-coke, subjecting the mixture containing semi-coke to compression to increase its apparent density and completing the carbonization of densified mixture.

3. Process of preparing phosphorus reduction furnace charging stock which comprises heating a mixture of fine phosphate rock and fine silica to a temperature below the sintering point of the mixture, adding hot fine coking coal to the hot unsintered mixture offine phosphate rock and fine silica, mixing the coal, phosphate rock and silica until the mixture contains semi-coke and subjecting the mixture containing semi-coke to compression to increase its apparent density.

4. Process of preparing phosphorus reduction furnace charging stock which comprises heating a mixture of fine phosphate rock and fine silica to a temperature below the sintering point of the mixture, adding fine coking coal to the hot unsintered mixture of fine phosphate rock and fine silica, mixing the coal, phosphate rock and silica until the mixture contains semi-coke and subjecting the mixture containing semi-coke to com- .pression to increase its apparent density.

5. Steps in process of preparing phosphorus reduction furnace charging stock which comprise adding hot fine coking coal to a hot unsintered mixture of fine phosphate rock and fine silica and mixing the coal, phosphate rock and silica until the mixture contains semi-coke.

6. Steps in process of preparing phosphorus reduction furnace charging stock which comprise adding fine coking coal to a hot unsintered mixture of fine phosphate rock and fine silica and mixing the coal, phosphate rock and silica until the mixture contains semi-coke.

'7. Process of agglomerating fine phosphate rock which comprises heating the fine phosphate rock to 850 to 1000 C., heating fine coking coal to 125 to 170 0., adding the hot fine coking coal to the hot fine phosphate rock, mixing the coal and phosphate rock until the mixture contains semi-coke, passing the mixture containing semicoke between rolls to increase its apparent density and completing the carbonization of densified mixture.

aoaasoo' I and phosphate rock untii'the mixture contains 18. Process of agglomerating fine phosphate rock which comprises heating the fine phosphate rock to atemperature below thesintering point 'of the rockfiheating fine coking coal, adding the hot fine coking; coal tonthe hot unsintered fine phosphate rock, mixingthe coal and phosphate rockuntil the mixture contains semi-coke, subjecting the'r'nixture' containing semi-coke to com}- I i pression toincrease its apparent density and 7 completing the carbonization ot densified mixture. n 9,1?rocess of 'agglomerating fine phosphate rock which comprises heating the fine phosphate rock to atemperature below the of the rock, heating finecoking coal, adding the hot fine coking coal to the hot unsintered fine phosphate rock, mixing the coal, and phosphate rockguntil the mixture contains semi-coke and subjecting the mixture containing semi-coke to compression to increase'its apparentjdensity, 1

iosProcess' of 'agglomerating fine 1 unsintered fine phosphate rock, mixing the coal sintering point phosphate rock which comprises heatingtheifine phosphate 7 :1 rock to a temperature below the sintering point oi the rock, adding hot fine coking coal to the'hot,

semi-coke and subjecting the mixture containing semi-coke to compression to increase its apparent density. i

11; Process of aggiomerating fine phosphate 5 rockwhich comprisesheating the fine phosphate rock to a temperature below the sintering point of the rock, adding fine coking coal to the hot, unsintered fine phosphate rock, mixing the coal and phosphate rock until the mixture contains semi- 10 coke and subjecting-the mixture containing semicoke to compression to increase its apparent density. V 12. Steps in process of agglomerating fine cokingcoal to the hot, unsintered fine phosphate rock and mixing the coal and phosphate rock until the mixture contains semi-coke. n s

13. Steps in process of agglomerating fine phosphate rock which comprise addingifine cok- 2 ing coal to the hot. unsintered' fine phosphate rock and mixing the coal and phosphate rock until the mixture contains semi-coke. I v v HARRY A. CURTIS.

ARMAND J. ABRAMS. 25

phosphate rockwhich comprise adding hot fine 15 I 

